Nutrient Cycles PDF

Nutrient Cycles and Biogeochemical...

Nutrient Cycles and Biogeochemical Cycling Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 1  The Movement of Matter After this section you should be able to: describe how water cycles within ecosystems. explain how carbon cycles within ecosystems. describe how nitrogen cycles within ecosystems. explain how phosphorus cycles within ecosystems. discuss the movement of calcium, magnesium, potassium, and sulfur within ecosystems.  Matter cycles through the biosphere Biosphere- The combination of all ecosystems on Earth. Biogeochemical cycles- The movement of matter within and between ecosystems involving biological, geologic and chemical processes.  About 25 of the 92 natural elements are known to be essential to life. Carbon (C), oxygen (O), hydrogen (H), and nitrogen (N) make up 96% of living matter. CHONPS is an acronym for the most important elements in living things, including the first four mentioned as well as phosphorous (P) and sulfur (S). Elements are composed of atoms that have a positive nucleus of protons and neutrons surrounded by a negative electron cloud. DOE Although ecosystems receive an inexhaustible influx of solar energy, chemical elements are available only in limited amounts and must be continually recycled. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 4 Objectives/EKs/Skills  The Hydrologic Cycle The movement of water through the biosphere. The oceans have 97.4% of the planet’s water and cover 75% of the earth’s surface. The remaining 2.8% is divided among rivers, lakes, groundwater, aquifers, and the greatest amount is locked in glaciers and polar ice. We are not running out of water, but we are not returning it to the cycle in usable condition.  The Hydrologic Cycle Transpiration- The process where plants release water from their leaves into the atmosphere. Evapotranspiration- The combined amount of evaporation and transpiration. Runoff- When water moves across the land surface into streams and rivers, eventually reaching the ocean. Objectives/EKs/Skills The Carbon Cycle  The Carbon Cycle is directly related to the oxygen cycle because much of the carbon on earth is in the form of carbon dioxide, and carbon monoxide gasses, as well as an ionic form called carbonate that is derived from carbon dioxide. The carbon atom is unique because it contains four electrons in it’s outer energy level, allowing it to bond easily to form four DOE additional covalent molecular bonds. These bonds are often with other carbon atoms, hydrogen, oxygen, nitrogen, sulfur and phosphorous. A compound containing carbon is referred to as organic. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 11  Much of the carbon dioxide is removed from the atmosphere by plants and other photosynthetic organisms who convert it to organic biomass. Most of the carbon dioxide in the atmosphere is taken in to the cells of small marine organisms who convert it to calcium carbonate for their shells. When carbon dioxide is removed from the atmosphere, it is called a carbon sink. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 12  The carbon cycle is greatly affected by the oceans as a major carbon sink. When ocean levels are higher, there are more algae to absorb the CO2. This NOAA graphic illustrates carbon dioxide levels based on both atmospheric testing, using ice cores, tree trunks and fossil evidence. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 13  Section 4-1 Burning fossil fuels and Greenhouse Effect wood and deforestation all increase CO2 in the Sunlight atmosphere, which increases the amount of Some heat escapes heat trapped. Heat does into space not escape into space. Problems-climate Greenhouse gases trap changes for organisms some heat that live in cooler ecosystesm, melting Atmosphere glaciers and flooding Earth’s surface  Practice FRQ 1.4 Identify one process in the diagram that happens quickly and one process that happens slowly. Explain how the rate at which fossil fuels are transferred into the atmosphere, as shown in the diagram, has altered the carbon cycle during the past 250 years. Objective/EKs/Skill The Nitrogen Cycle  The Nitrogen Cycle converts nitrogen gas into useable compounds for life. Nitrogen is the second most abundant element in the human body and 78 % of the earth’s atmosphere. Nitrogen gas itself is extremely stable and does not react with other compounds without extreme heat or electricity (from lightning in the air) or a specific enzyme found in certain plant bacteria. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 18  N2 gas must be “fixed” by Rhizobium bacteria using the enzyme nitrogenase. This process binds N2 with H2 to form NH4+ Ammonium ion. This chemical can be absorbed into the roots of plants and used to synthesize proteins which convert ammonium into amines NH2. EPA Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 19  Other bacteria are called nitrifying bacteria and they convert the ammonia into nitrates NO3 that are freely absorbed by plants through the water. Nitrification Reaction Sequence NH4 NO2 NO3 Other bacteria are called denitrifying bacteria and they convert the nitrates back into atmospheric nitrogen. Denitrification Reaction Sequence NO3 NO2 NO N2O N2 Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 20  Practice FRQ 1.5 Describe one chemical transformation that occurs in the natural nitrogen cycle and explain the importance of that transformation to an ecosystem. Objective/EKs/Skill The Phosphorus Cycle Phosphorus is most commonly found in rock formations and ocean sediments as phosphate salts. Phosphate salts that are released from rocks through weathering usually dissolve in soil water and will be absorbed by plants. Phosphorous does not become gas. It cycles among organisms and between organisms and the soil.  The Phosphorus Cycle often contains phosphorous bound into minerals in rock or sediments in the oceans, in the form of phosphates. Phosphates combined with carbon compounds like DNA are called organophosphates. They are important factors in the production of energy molecules like ATP and hydrogen carriers like NADP, making phosphorous a macronutrient in plants. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 25  Phosphates often runoff from farmlands and pastures into adjacent waterways causing eutrophication. When fertilizers increase quickly in water, there is often an algae bloom (rapid growth) that may eventually cause the water to become anoxic. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 26  Sulfur may be found mineralized in the ground. When sulfur compounds are eroded from rocks and minerals, they may be dissolved in water to form acids, or react with oxygen to form sulfur oxides. When sulfur oxides combine with water in the atmosphere, acid precipitation is produced. Sources of sulfur come from burning coal and other fossil fuels with high sulfur content, especially in power plants. Volcanoes and undersea vents are naturally occurring sources of sulfur oxides. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 27  Practice FRQ 1.6 Choose 2 reservoirs depicted in the diagram above and show how phosphorus moves from one to the other Check your understanding 1. Which of the following is fixed from the atmosphere by bacteria? a. magnesium b. phosphorous c. sulfur d. nitrogen e. potassium 2. The largest carbon pool is found in a. oceans b. the atmosphere c. sedimentary rock d. living organisms e. fossil fuels 3. Haitian farmers are buying mango tree saplings for $10 each and full grown trees produce $75 of fruit each year. If a farmer wishes to earn $1500 per year when the trees are grown, how much will the farmer have to spend on saplings? a. $100 b. $150 c. $200 d. $750 e. $1000 Biomes 1.2 and 1.3 Objectives/EKs/Skill Global Processes Determine Weather and Climate Weather- the short term conditions of the atmosphere in a local area. These include temperature, humidity, clouds, precipitation, wind speed and atmospheric pressure. Climate- The average weather that occurs in a given region over a long period- typically several decades. Variations in Climate Determine the Dominant Plant Growth Forms of Terrestrial Biomes Climate affects the distribution of species around the globe. Organisms possess distinct growth forms due to adaptations to local temperature and precipitation patterns. Biomes- The presence of similar plant growth forms in areas possessing similar temperature and precipitation patterns.  Biomes by Millimeters of Rainfall Per Year 5000 4500 > 10,000 mm 4000 Maximum Rainfall 3500 Minimum Rainfall mm of rainfall/year 3000 2500 2000 1500 1000 500 0 Desert Tundra Taiga Grassland Deciduous Rainforest Forest Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 5  Biomes by Net Primary Productivity Per Year 10000 9000 8000 Kilocalories/meters 7000 square/year 6000 5000 4000 3000 2000 1000 0 Desert Tundra Taiga Grassland Deciduous Rainforest Forest Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 6  Tundra Cold, treeless biome with low-growing vegetation. In winter, the soil is completely frozen. The tundra's growing season is very short, usually only about 4 months during summer. The underlying subsoil, known as permafrost is an impermeable, permanently frozen layer that prevents water from draining and roots from penetrating. Tundra  Boreal Forest Forests made up primarily of coniferous (cone- bearing) evergreen trees that can tolerate cold winters and short growing seasons. Boreal forests are found between about 50˚ and 60˚ N in Europe, Russia and North America. This subarctic biome has a very cold climate, and plant growth is more constrained by temperature than precipitation. The soil is nutrient-poor due to slow decomposition. Boreal Forest  Temperate Rainforest Moderate temperatures and high precipitation typify the temperate rainforest. The temperate rainforest is a coast biome and can be found along the west coast of North America from northern California to Alaska, in southern Chile, on the west coast of New Zealand, and on the island of Tasmania. The ocean currents help moderate temperature fluctuations and provide a source of water vapor. This biome has a nearly 12-month growing season where winters are rainy and summers are foggy. The mild temperatures and high precipitation supports the growth of very large trees. Temperate Rainforest  Temperate Deciduous Forest Receive over 1 m (39 inches) of precipitation annually. Found in the eastern United States, Japan, China, Europe, Chile and eastern Australia. Dominated by broadleaf deciduous trees such as beech, maple, oak and hickory. Warmer summer temperatures favor decomposition so soils generally contain more nutrients than those of boreal forests. Temperate Deciduous Forest  Woodland/Shrubland Found on the coast of southern California, southern Australia, southern Africa and in the area surrounding the Mediterranean Sea. Hot, dry summers and mild, rainy winters are characteristic of this biome. There is a 12-month growing season, but plant growth is constrained by low precipitation in summer and by relatively low temperatures in winter. Wildfires are common and plants of this biome are well adapted to both fire and drought. Woodland/Shrubland  Temperate Grassland/Cold Desert This biome has the lowest average annual precipitation of any temperate biome. These are found in the Great Plains of North America, in South America, and in central Asia and eastern Europe. Cold, harsh winters and hot, dry, summers characterize this biome. Plant growth is constrained by both insufficient precipitation in summer and cold temperatures in winter. Plants include grasses and non woody flowering plants that are well adapted to wildfires and frequent grazing by animals. Temperate Grassland/Cold Desert  Tropical Rainforest In the tropics, average annual temperatures exceed 20˚C. This biome is located approximately 20˚ N and S of the equator. They are found in Central and South America, Africa, Southeast Asia, and northeastern Australia. Precipitation occurs frequently and this biome is warm and wet with little temperature variation. Tropical rain forests have more biodiversity per hectare than any other terrestrial biome and contain up to two-thirds of Earth's terrestrial species. Tropical Rainforest  Tropical Seasonal Forest/Savanna Warm temperatures and distinct wet and dry seasons characterize this biome. Tropical seasonal forests are common in much of Central America, on the Atlantic coast of South America, in southern Asia, in northwestern Australia, and in sub-Saharan Africa. Soil in this biome is fairly fertile and can be farmed due to high decomposition rates, but the low amount of precipitation constrains plants from using the soil nutrients that are released. Grasses and scattered deciduous trees are common. Tropical Seasonal Forest/Savanna  Subtropical Desert This biome is found at 30˚ N and S with hot temperatures and extremely dry conditions. The Mojave Desert in the southwestern United States, the Sahara in Africa, the Arabian Desert of the Middle East and the GReat Victoria Desert of Australia are all subtropical deserts. Cacti, euphorbs and succulent plants are well adapted to this biome. Subtropical Desert Prescribed fires actually help some trees germinate, and are used to manage resources by clearing underbrush and litter that may fuel a larger fire later. Wildfires are caused by people burning debris, camping, smoking, arson and lightning. Photo courtesy of John McColgan, Alaska Forest Service The Forest Service’s policy is to let surface wildfire in wilderness areas burn. Fires are fought if they threaten people, slow tourism or may damage property. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 25  Some people argue that fire suppression has allowed the forests to become tinderboxes. Others say that the cost of fighting fires and the risks to firefighters is not worth the costs. While others disagree with all prescribed burning. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 26 Check your Understanding 1. Permafrost is an important factor in which of the following biomes? I. Tundra II. Boreal forest III. Cold desert a. I only b. I and II only c. II only d. I and III only e. III only 2. Plant growth in which of the following biomes is primarily constrained by precipitation? a. Boreal forest b. Temperate seasonal forest c. Temperate grassland d. Tropical rainforest e. Tundra 3. Which of the following biomes has the highest soil nutrient levels? a. tropical rainforest b. temperate rainforest c. boreal forest d. woodland/shrubland e. temperate seasonal forest Practice FRQ 1.2 Identify one characteristic of a biome and explain how that characteristic determines the community of organisms found in that biome  Aquatic Biomes- characterized by depth and salinity After reading this section you should be able to: identify the major freshwater biomes. identify the major marine biomes.  Water Basics 30 Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point Objectives/EKs/Skills  Aquatic Ecosystems 1. Freshwater - Flowing water - Standing water - Wetlands 2. Estuaries: Wetlands formed where rivers meet the ocean. Estuaries contain a mix of fresh and saltwater. 3. - Rich community of organisms 4. Marine - Intertidal - Coastal  Freshwater Ecosystems Potomac River Flowing water: organisms adapted to the rate of flow river, stream, creek, brook Standing Water: lake, pond, reservoir Wetlands: ecosystem in Lake which water covers the soil for at least part of the year bog, marsh, swamp Swamps Great Dismal Swamp, Va  The Chesapeake Bay Chesapeake Bay Watershed is the largest estuary in the United States  Streams and Rivers Flowing fresh water that may originate from underground springs or as runoff from rain or melting snow. Streams are typically narrow and carry relatively small amounts of water where rivers are usually wider and carry larger amounts of water.  Lakes and Ponds Standing water that some of which is too deep to support emergent vegetation. Lakes are larger than ponds but there is no clear point at which a pond is considered large enough to be called a lake. Lakes and Ponds  Lakes and Ponds Littoral zone- the shallow area of soil and water near the shore where algae and emergent plants grow. Limnetic zone- open water, where rooted plants can no longer survive. Phytoplankton are the only photosynthetic organisms. This zone extends to as deep as sunlight can penetrate. Profundal zone- the zone where sunlight cannot penetrate and therefore producers cannot survive. Benthic zone- the muddy bottom of a lake or bond beneath the limnetic and profundal zone.  Freshwater Wetlands Aquatic biomes that are submerged or saturated by water for at least part of each year, but shallow enough to support emergent vegetation. These include swamps, marshes, and bogs.  Wetlands are valuable Wetlands are extremely valuable for wildlife and have a lot of biodiversity They are breeding grounds for many animals They slow runoff, reduce flooding, recharge aquifers, and filter pollutants People have drained wetlands, mostly for agriculture Southern Canada and the U.S. have lost over half of their wetlands  Salt Marshes Found along the coast in temperate climates and contain non woody emergent vegetation. The salt marsh is one of the most productive biomes in the world.  Mangrove Swamps Found along tropical and subtropical coasts and contain trees whose roots are submerged in water. Mangrove trees are salt tolerant and help protect the coastlines from erosion and storm damage.  Marine Ecosystems Intertidal: Tidal regions. Organisms exposed to air Coastal: Below the tidal zone along the coast Open Ocean Coral Reef: warm, tropical shallow waters. Most productive ocean area  Marine (Salt Water) Aquatic Zones Characteristics: Nitrogen and carbon dioxide are the most abundant dissolved gases. The oceans are called carbon sinks because of their ability to hold this gas. Ocean phytoplankton produce much of the atmospheric oxygen. Dissolved salts primarily chloride and sodium and minerals give it an average pelagic salinity of 35 PPT. Fairly constant pH of 7.4 – 8.0 46  Intertidal Zone Narrow band of coastline that exists between the levels of high tide and low tide. Waves that crash onto the shore in this biome can make it a challenge for organisms to hold on and not get washed away. Figure 4.33  The Open Ocean The depth that light can penetrate in the open ocean is dependent on the amount of sediment and algae suspended in the water. Photic zone- the zone that receives enough light to allow photosynthesis to occur. Aphotic zone- the deeper water that lacks sufficient light for photosynthesis. Chemosynthesis- The process that occurs in the aphotic zone when some species of bacteria use methane and hydrogen sulfide to generate energy.  Coral Reefs Found in warm, shallow waters beyond the shoreline. Earth's most diverse marine biome even though coral reefs are found in water that is relatively poor in nutrients and food. Coral bleaching- when the algae inside the coral dies. Scientists believe this is due to a combination of disease and environmental change. Check your understanding 1. Most of the photosynthesis in lakes and ponds occurs in the a. benthic zone b. littoral zone c. limnetic zone d. profundal zone e. aphotic zone 2. Aquatic biomes are categorized by which of the following? I. Dominant plant growth II. Depth III. Salinity a. I and II only b. I and III only c. II and III only d. III only e. I, II and III Check your understanding 3. Which of the following is NOT an important ecosystem service provided by wetlands? a. flood control b. breeding habitat for birds c. migratory habitat for birds d. water filtration e. seed dispersal 4. Which biome contains the aphotic zone? a. coral reefs b. mangrove swamps c. streams and rivers d. freshwater wetlands e. open ocean Practice FRQ 1.3 Identify an organism found in an aquatic biome and explain how that organism is uniquely adapted to live in that biome. 1.1 Ecosystems Objectives/EKs/Skills Nature exists at several levels of complexity Interactions 1: Competition Competition occurs when 2 organisms try to use the same ecological resource (food, nesting area, mate, etc.) No two species can occupy the same niche. This is known as the Competitive Exclusion Principle.  Competition Competition- the struggle of individuals to obtain a limiting resource. No two species can occupy the same niche. This is known as the Competitive Exclusion Principle. Resource Patitioning  Interactions 2: Predation Predation: One organism captures and feeds on another Predator: the organisms that does the killing (killer) Prey: The food organism, the one that gets eaten (killed)  Predation Predation- the use of one species as a resource by another species. True predators- kill their prey. Herbivores- consume plants as prey. Parasites- live on or in the organism they consume. Parasitoids- lay eggs inside other organisms.  Interactions 3: Symbiosis Symbiosis: relationship in which 2 species live closely together There are 3 main types of symbiosis: A. Mutualism B. Commensalism C. Parasitism  Mutualism Mutualism- A type of interspecific interaction where both species benefit.  Mutualism Examples Flowers and pollinators: Flowers provide food and pollinators help them reproduce The bacteria Rhizobium (nitrogen fixation) and the roots of legume plants (beans-type of plants) Egyptian Plover eats parasites (gets food), Crocodile gets rid of parasites.  Commensalism Commensalism- a type of relationship in which one species benefits but the other is neither harmed nor helped.  Commensalism Ex’s Clownfishes live in of sea anemones; most predators avoid the poisonous tentacles and the fishes are protected Some tropical orchids use trees or branches of trees for support without harm or benefit to the tree. Remoras attach to sharks. Remoras do not injure or benefit the shark, but enjoy the shark's protection and live on food scraps  Parasitism Parasitism: One organisms lives on or inside another and “harms” it. The parasite obtains most its food from the host. Tapeworms, fleas, ticks, heartworms.  Keystone Species Keystone species- a species that plays a role in its community that is far more important than its relative abundance might suggest. Practice what you know 1. Resource partitioning a. occurs in mutualism b. can occur through morphological differences between competing species c. can cause the extinction of a competing species d. is not the result of behavioral changes e. does not occur among competing predators 2. Which interaction harms both species involved? a. competition b. predation c. parasitism d. mutualism e. commensalism Practice FRQ 1-identify two organisms that compete for a shared resource. Describe how resource partitioning could reduce the competition between the two organisms you identified. Energy Flow in an Ecosystem  Energy Objectives After this section you should be able to: describe the processes of photosynthesis and respiration distinguish among the trophic levels that exist in food chains and food webs. quantify ecosystem productivity. explain energy transfer efficiency and trophic pyramids.  Ecosystem Ecology Examines Interactions Between the Living and Non-Living World Ecosystem- A particular location on Earth distinguished by its particular mix of interacting biotic and abiotic components. Biotic-living factors that affect the ecosystem Abiotic-non living factors that affect the ecosystem (sun, soil, wind, water) Objective/EKs/Skill  Photosynthesis Producers (autotrophs) are able to use the suns energy to produce usable energy through the process called photosynthesis.  In photosynthesis, plants convert radiant energy into chemical energy in the form of glucose sugar. Sunlight Carbon Glucose dioxide Water Carbon from carbon dioxide is combined with hydrogen from water molecules to form organic compounds like sugars. This carbon production is referred to as biomass. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 6  Respiration Cellular respiration is the process by which other organisms gain energy from eating the tissues of producers.  When cells utilize organic compounds they produce carbon dioxide and water as the products of cell respiration. These same two molecules are used by photosynthesis. Chemical energy and heat energy are normal products of respiration that recycle in the environment. Mitochondria are the organelles in eukaryotes where oxygen is used to finish oxidative respiration. NSF NASA Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 9  The tropical oceans are important carbon “sinks” where carbon dioxide can be absorbed from the atmosphere. Microscopic foraminifera use tons of CO2 to compose their shells or tests. Photo: National Biological Information Infrastructure Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 10  Gross primary production (GPP) represents all of the organic compounds produced by photosynthesis. When the organic compounds used through cellular respiration are subtracted, the result is net primary production (NPP). Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 11  As energy flows through each step of a food web, it becomes more unusable. The rate of conversion of solar energy into chemical energy is the amount of energy available, calculated as productivity. Gross productivity - respiration = net productivity given in units of g/m2/yr. G–R=N Biomass is the dry weight of all organic matter in living organisms it is used to estimate gross productivity. Respiration is the rate of energy used at each level to maintain life (estimated at 90% of the available calories). Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 12 Practice FRQ 1.8- Describe the process of net primary productivity (NPP). Describe the relationship between primary productivity and biodiversity.  Instrumental Values of Ecosystems Provisions- Goods that humans can use directly. Regulating services- The service provided by natural systems that helps regulate environmental conditions. Support systems- The support services that natural ecosystems provide such as pollination, natural filters and pest control. Resilience- Resilience of an ecosystem ensures that it will continue to provide benefits to humans. This greatly depends on species diversity. Cultural services- Ecosystems provide cultural or aesthetic benefits to many people.  Energy Transfer Efficiency and Trophic Pyramids Biomass- The energy in an ecosystem is measured in terms of biomass. Standing crop- The amount of biomass present in an ecosystem at a particular time. Ecological efficiency- The proportion of consumed energy that can be passed from one trophic level to another. Trophic pyramid- The representation of the distribution of biomass among trophic levels. Objective/EKs/Skill  The ocean is the largest producer on the planet because of the amount of phytoplankton or algae. Only about 10% of the available energy from producers is available for the primary consumers. 10% of primary consumer’s calories 10% of 10% of producer’s secondary calories calories Fraction of sun’s energy Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 18  Tropical rainforest biomes are almost as productive as salt marsh estuaries when calculating the biomass per square meter. Biome Net Productivity 2500 2000 Grams Per Square Meter Per Year 1500 1000 500 0 Tropical Rainforest Deciduous Forest Boreal Forest Savanna Grassland Desert Biom e Type Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 19  Although energy appears to be “lost” from one trophic level to the next, the First Law of Thermodynamics or the Law of Conservation of Energy is maintained. First law of thermodynamics A physical law which states that energy can neither be created nor destroyed but can change from one form to another. Second law of thermodynamics The physical law stating that when energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes Some energy is wasted with death and decay, while other energy is used by organisms who are decomposers or detrivores. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 20  Food chains and food webs can become complicated. USGS Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 21  In ecosystems, energy is cycled through these niches: Autotrophs - produce food by photosynthesis Heterotrophs - consume autotrophs and other heterotrophs Decomposers - rearrange organic materials into nutrients for autotrophs The amount of energy available to support life is called the carrying capacity. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 22  Food chains represent the steps in transferring energy through the ecosystem. Arrows indicate the direction of flow of energy from prey to predator or plant to animal. Complex and integrated food chains are called food webs. The most common population in a community is called the dominant. The food web is built around organisms called critical biomass or keystone species. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 23  Energy transfer can be representations by trophic pyramids that compare the number of organisms in a population, or the weight (biomass) of organisms, or the productivity (energy calories). Biomass Pyramid Trophic Pyramid Numbers Pyramid Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 24  The amount of energy changes even though energy is never created or destroyed because: 1. Energy is converted into unusable forms such as heat. Warm-blooded animals are “expensive” in an ecosystem because they consume more calories to maintain body heat. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 25  2. Energy is converted for an organisms’ own respiration, metabolism, digestion and predation. USDA 3. Parts of an organism, such as bones and scales, do not provide calories. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 26 If one trophic level has 100,000 calories available, only 10,000 can potentially be transferred to the next trophic level. The more levels in the trophic pyramid the less energy is available in a usable form at the next higher level. Shorter food chains are more efficient, but they lack diversity. 27  Check your understanding 1. A zebra is an example of a. a secondary consumer b. a producer c. a detritivore d. a primary consumer e. a scavenger 2. The average efficiency of energy transfer between trophic levels is approximately a. 1% b. 4% c. 10% d. 40% e. 50% 3. The gross primary productivity of an ecosystem is a. the total amount of biomass b. the total energy captured by photosynthesis c. the energy captured after accounting for respiration d. the energy available to primary consumers e. the biomass of the producers 4. Ecosystem boundaries are a. based primarily on topographic features b. boundaries to nutrient flows c. never based on human created features d. are only used for ecosystems smaller than a few square hectares e. depend on many subjective factors  Practice FRQ 1.11 Describe one direct effect that a decline in the frog population would have on the food web. Identify an organism that is both a secondary and tertiary consumer